Shielding sensitive signals from magnetic flux is often necessary to avoid unexpected behaviors in circuits. Typically, for relatively low-frequency magnetic fields, metal shielding structures can be used to prevent magnetic flux from adversely affecting circuits and signals within and between circuits. This is because the effectiveness of shielding (i.e., the skin effect or depth to which magnetic flux can penetrate) is based in part on frequency.
As the frequency of the magnetic flux increases, so does its depth of penetration into metal shielding structures. While the efficacy of metal shielding of high frequency fields can be improved by increasing the thickness of the shield structure, such increased shield thickness can be impractical and costly in terms of material and space.
Magnetic field sensors generally use one or more magnetic field sensing elements in combination with other circuitry to detect magnetic fields for various purposes, such as to detect movement of a target, angular position of a target, proximity of a target, or a current through a conductor. It will be appreciated that based on this sensing methodology, accurate detection of only intended magnetic fields and immunity to detection of stray and other unintended fields is critical to accurate operation of magnetic field sensors.